Surgical procedures, both human and veterinary, often require the fixation of soft tissue. One common example is anterior cruciate ligament (ACL) reconstruction. ACL reconstruction exemplifies the problems often associated with surgical fixation. A significant fraction of patients—as high as 40%—experience unsatisfactory outcomes caused by tension loss during implantation, or by post-operative cyclical loading. It is important for the surgeon to be able to accurately estimate and maintain tissue tension and stability. However, the surgeon's ability to estimate and maintain tissue tension can be compromised by implants whose installation requires multiple steps. During the fixation procedure, many conventional devices provide inconsistent tissue tensioning, and a loss of tension often results. Post-operative slippage at the fixation site also contributes to the problem. The holding strength of many conventional devices is insufficient to prevent tissue slippage during the initial post-operative period. Current standards for post-operative rehabilitation call for strong initial fixation. However, it is difficult if not impossible for many conventional devices to achieve sufficiently strong fixation.
Conventional technologies for the fixation of soft tissues (e.g., tendon) to anatomical structures with comparable or greater strength and stiffness (e.g., bone) has relied primarily on variations of traditional hardware devices such as screws, washers, staples, pins, and the like. Such conventional devices are ineffective at maintaining tissue tension during tissue fixation. Nor do they permit incremental and stable adjustments to tissue tensioning during the process. Conventional devices often require a patient to undergo multiple procedures, procedures that are often specific to the particular device employed, that are usually extraneous to the primary surgical procedure, and that would otherwise be unnecessary. Where bone tunnels are used, conventional devices are often located some distance from the tunnel. A substantial disadvantage of nearly all prior devices is that they do a poor job of maintaining the proper tension while the soft tissue is secured. No previous device known to the inventor permits the convenient, incremental, reversible, securely-maintained application of tissue tension during the affixing process.
Limitations of many conventional devices include: the time required for installation; otherwise extraneous procedures needed for device installation; unreliable tissue holding strength; loss of tissue tension during the affixing procedure; and the expense of acquiring and maintaining specialized application equipment that often has no other use.
Amis et al., patent application publication no. US 2011/0112640 discloses a graft fixation device for fixing a ligament graft to a bone. The device comprises a locating means for locating the device in the bone and a graft support means arranged to support the graft, wherein the graft support means allows adjustment of the position of the graft relative to the bone. The graft support means may be rotated to provide adjustment. Alternatively the graft support means may be arranged to slide axially or to move radially to provide adjustment.
May et al., U.S. Pat. No. 5,108,433 discloses a prosthetic device for replacing a ligament or tendon. An adjustable connector allows tension on the ligament to be increased or decreased. Three embodiments of the adjustable connector are described: one employs a pin with a threaded shaft and a cylinder with a threaded bore, one employs a ratchet plate and a spool, and one employs cleats.
Johnson, U.S. Pat. No. 5,562,668 describes a screw tensioning device for holding one end of a ligament graft.
ElAttrache et al., U.S. Pat. No. 6,544,281 discloses a method for securing soft tissue to bone. A blind hole or socket is created in the bone at the location the graft is to be secured. Preferably, suture is then passed through the graft at desired points. A cannulated driver is pre-loaded with a cannulated plug or screw slidably disposed onto the distal portion of the driver. The driver is inserted into the hole with the screw or plug just outside the hole. Tension is then placed on the suture. Once adequate tension is achieved on the suture, the driver is pressed into the hole, which engages the first thread or bump of the screw or plug on the bone. The screw or plug is then fully advanced into the hole using the driver.
Lopez and Monroe, U.S. Pat. No. 8,603,115 discloses a soft tissue fixation device for use in ACL or CCL reconstruction. A base member has a passageway extending perpendicularly from the top surface through the bottom surface. The passageway is sized to allow soft tissue to be inserted through it. An affixing member is attachable to the base member. The base member has a notched section in the top surface extending from the passageway to a first perimeter section of the base member sized to accommodate at least a portion of the graft. The base member is secured to bone. The base member is also provided with a sleeve whose interior wall surfaces form a part of the passageway and is sized to be inserted into the bone opening. The affixing member is provided with a series of teeth members extending downward from its lower surface. The teeth members are positioned so that when the affixing member is attached to the base member the teeth members will extend across and into the notched section of the top surface of the base member. The opposite ends of the affixing member are shaped to fit into aligned notches positioned along perimeter sections of the base member bottom surface for attaching the clip member to the base member.
See also: Lopez M J, Monroe W T. Initial Femoral Fixation Properties of One Novel and Two Established Devices in Canine Cranial Cruciate Ligament Reconstruction, Proceedings American College of Veterinary Surgeons Annual Symposium E15, 2006. (Abstract); Lopez M J, Borne A, Monroe W T, Bommala P, Kelly L, Zhang N. Novel anterior cruciate ligament graft fixation device reduces slippage. Med Devices (Auckland) 6:59-68, 2013; Lopez M J, Casey J P, Spencer N D, Monroe W T. Initial femoral fixation properties of one novel and two established devices in canine cranial cruciate ligament reconstruction. 41st American College of Veterinary Surgeons Annual Symposium, Washington D.C., Oct. 4-7, 2006 (Poster); Lopez M J, Casey J P, Spencer N D, Monroe W T. Biomechanical characteristics of an implant used to secure semitendinosus-gracilis grafts in a canine model of extra-articular anterior cruciate ligament reconstruction. Vet Surg 36:599-604, 2007; Lopez M J et al., “In vivo application of novel and commercially available bioabsorbable implants for tibial fixation of cranial cruciate ligament reconstruction grafts”. 45th American College of Veterinary Surgeons Meeting, Chicago, Ill., Nov. 5, 2011. (Presentation)
Hoof, U.S. Pat. No. 8,540,734 discloses an adjustable, stand-alone tensioning system that allows an operator to provide adjustable tension to a suture during surgery, using a spring mechanism. The device is evidently designed to be used as a tool during surgery, but not to be implanted and to remain in a patient after surgery. The device is evidently designed to apply tension to a suture, rather than directly to a graft tissue.
L. Bodó et al., “Development of a tension-adjustable implant for anterior cruciate ligament reconstruction,” Joint Dis. Rel. Surg., vol. 19, pp. 27-32 (2008) discloses a “loop-in-loop” technique for anterior cruciate ligament reconstruction. The implant contains two parts: a plastic strap with a smooth inner surface and a serrated outside surface; and a plastic ring with a serrated latch. The two serrated surfaces of the two parts allow one-way movement of the plastic strap in the ring to adjust tightening of the graft.